Mathematical modeling of direct ethylene glycol fuel cells incorporating the effect of the competitive adsorption

Abstract

In this work, a one-dimensional mathematical model for a direct ethylene glycol fuel cell using hydrogen peroxide as oxidant is developed. This model considers the ethylene glycol crossover and the competitive adsorption between ethylene glycol molecules and hydroxyl ions at reaction sites, in addition to mass/charge transport and electrochemical reactions. In addition, the complicated co-existence of the hydrogen peroxide reduction reaction, the hydrogen peroxide oxidation reaction, and the oxygen reduction reaction in the cathode is also considered in this model. The mathematical model under the consideration of the above-mentioned physicochemical processes exhibits a good agreement with experimental results. In addition, the effects of various operating and electrode structural parameters on the cell performance are examined, including concentrations of various species, the exchange current densities and the thicknesses of diffusion layer. The numerical results exhibit that the cell performance improves with the increasing concentrations of hydrogen peroxide and sulfuric acid. As for the ethylene glycol and hydroxyl ions, increasing the concentrations makes contribution to higher performance, while the cell performance experiences a degradation at a high current density region due to the remarkable ohmic loss. The model also shows that increasing both the anode and cathode exchange current densities leads to an improved cell performance, which indicates the significance of developing novel catalyst with superior catalytic activity. Moreover, the effect of the structural design parameters of the anode and cathode diffusion layer is also investigated, and the results show that increasing thickness of diffusion layers has a negative effect on the cell performance.